The Canon 5D Mark III is surely an excellent camera and you should be happy with it.

The only problem with it is that the Canon 5D Mark III has a (not very good) sensor that does not match or even compare to the excellent sensor used on the Nikon D600 that has the same image quality than the one used on the Nikon D800 but at 24 MP instead of 36 MP.

Well, it is always hard to keep rational in front of a really big bargain price!